David Cameron is going to give a speech today with Lord Reid today about the AV referendum. In it, he will say:

“Too often debates about AV are less like political arguments, and more like scientific discussions, where people get lost in a language of proportionality and preferences, probabilities and possibilities.

“Of course, some of these things are important. But for me, politics shouldn’t be some mind-bending exercise. It’s about what you feel in your gut – about the values you hold dear and the beliefs you instinctively have. And I just feel it, in my gut, that AV is wrong.”

Just a reminder, this came from the Prime Minister of the United Kingdom, not a Richard Littlejohn column or some particularly stupid Comment is Free post. The man who directs a nation of 62 million people and controls the sixth largest economy in the world doesn’t think politics should be about thinking and weighing up different options. Oh no, that’s just “some mind-bending exercise”! No, politics is about what you feel in your gut* and your blind instincts.

Voting systems are, at heart, all about mathematics – each voting system is just a different way of counting people’s opinions. You cannot discuss any voting system without taking into account the way it behaves mathematically. The language of “proportionality and preferences, probabilities and possibilities” is not swamping the debate, it is the debate.

Imagine if this was any other debate. Imagine if David Cameron said we should ignore the clinical trials when deciding whether to fund a particular drug, or the climate models when considering pollution controls, on the grounds that all this scientific evidence was “mind-bending” and got in the way of his “instinctive beliefs”. No-one would think that was an appropriate way for an elected official to make decisions.

If you push the evidence out of the debate, all you’re left with is empty sloganising, blatant untruths and tribal party politics. Without a proper debate on the pros and cons of each voting system, the AV referendum just becomes a Cameron/Clegg popularity contest. That’s a terrible way to decide an issue that will shape government in the UK for decades to come.

* Most of what’s in your gut is digested food, so perhaps Cameron is just saying that politics should be full of shit?